Is There a Future for Lithium-Batteries as High Energy Density Source in Electrical Engine Vehicles ? Some Recent Trends

Abstract

Thanks to low weight and a bonding energy with oxygen exceeding that of sodium lithium rechargeable batteries should be the most realistic solution for electrically driven vehicles with a total capacity which can be four times that of the best so far known nickel-cadmium cells and the advantage of possible room temperature utilization. Lithium is also much safer as competing sodium in the eventuality of a crash.

The new batteries are based on “rocking chair” reactions involving at discharge diffusion from a lithium rich negative electrode through a flexible but stable electrolyte into a host structure playing the role of the positive electrode. The double intercalation process must be reversible on many cycles without significant capacity loses.

Lithium metal has been considered for a long time as the best anode material, but sensitivity to moisture and strong anodic volume shrinking at discharge represent serious drawbacks. Use of lithium intercalated “carbon blacks” is a seducing alternative as far appropriate materials selection could allow to exceed the present insertion limitation (∼ Li_0.7C₆) but with a wide composition range.

The choice of the positive electrode must meet several requirements : reversibility over a broad intercalation range, high electrochemical chain potential excluding indeed intermediate electrolyte oxidation (EMF below ∼ 4 v), absence of ageing harm. A few attractive solutions have been considered here : a new lithium-rich Li_xV₂0₅ phase, 2D-Li_xNi_1-yCo_y0₂ oxides. The physical behavior of these materials has been discussed as well as practical utilization in rechargeable batteries for electrical vehicles.

It appears that there will be no industrial achievement in the near future without imaginative and comprehensive fundamental research related to the user’s requirements.